Solid stare lasers have been used to generate ultrashort optical pulses. However, them are problems inherent with these lasers. The techniques utilized to generate these pulses have generally relied on sophisticated electro-optic modulation techniques or passive techniques which use organic dyes to initiate the pulse generation process. These active and passive techniques add complexity and potential hazards to the operation because of the additional components added to the system and the chemical dangers of organic dyes.
Existing starting mechanisms for passive mode-locked lasers have cost approximately $5,000. These staring devices have required spaces of approximately one foot per side for the space needed. External power supplies such as RF power and mechanically actuated pumps have generally been needed for these mechanisms.
Mode-locked diode lasers have may applications of which the inventors of this invention, specifically Dr. Peter Delfyett have well documented. U.S. patent Ser. No. 08/241,620 entitled "Self Starting Femtosecond Ti Saphire Laser with Intracavity Multiquantum Well Absorber" filed on May 12, 1994, by inventor Peter J. Delfyett now U.S. Pat. No. 5,434,873, and U.S. patent Ser. No. 08/236,373 entitled "Mode Locked Laser Diode in a High Power Solid Siam Regenerative Amplifier and Mount Mechanism" filed on May 2, 1994, and assigned to the same assignees as this invention, both of which are incorporated by reference describe applicable laser applications Dr. Delfyett has other "mode-locked" laser inventions which includes U.S. Pat. No. 5,265,107, issued on Nov. 23, 1993.
Current compact modelocked ultrafast lasers suffer from the necessity of requiring a fixed cavity length. This necessity prevents the user from having the flexibility of choosing an optimum pulse repetition frequency for a specific application.
The pulse repetition frequency of compact diode lasers tend to be large, typically on the order of 100 megahertz to several gigahertz, owing to the fast gain recovery time of semiconductor diode lasers. Thus, applications which require an ultrashort pulse laser source operating at a lower pulse repetition rate are required to rely on large, expensive ultrafast laser systems.
Methods for reducing the pulse repetition rate of modelocked ultrafast laser systems typically rely on electro-optic materials for producing a "Pockel's Cell" which acts as a fast shutter or optical gate. This device is relatively large (approximately 1 cubic foot) and requires large electric fields (voltages in order to operate.
In addition, some optical pulse slicers have a limited clear aperature, which increases the insertion loss of the device.
For integrated optic applications, i.e. incorporating a laser device, such as a semiconductor laser, with a dielectric optical gate is costly and cumbersome owing to the material mismatch employed with current dielectric optical gates or modulators. Modulating of data signals has been accomplished in the prior art. U.S. Pat. No. 5,136,598 to Weller et al. describes where an optical beam from a laser is modulated. However, Weller requires multiple components to operate, where the optical beam is first modulated by a dielectric material and then subsequently amplified with a semiconductor source. The subject invention does not require, or need dielectric materials to operate.
Thus, this invention reduces the problems inherent with current mechanisms.